1. Field of the Invention
The invention relates to means for sealing the upper end-adjacent portion of the rotatable agitator shaft of a chemical reactor vessel against the escape of gas, vapor, or liquid from the interior of the vessel along the agitator shaft.
2. Description of the Prior Art
U.S. Pat. No. 2,931,631 to E. S. Harrison discloses a mechanical sealing assembly and method of operation wherein a drive bearing is releasably secured to and carried by the upper flange of the outer shell of a mechanical stack-up type of seal assembly which engages the upper end-adjacent portion of an agitator shaft which projects upwardly from the flanged drive nozzle of a reactor vessel, said shell including a lower flange which is also securely, though releasably, anchored relative to the flanged drive nozzle of the reactor vessel. A pair of vertically spaced "abutments" are formed on the agitator shaft and extend radially outward therefrom, and a pair of oppositely aligned spring-receptive metal cages are carried by the agitator shaft in spaced relationship with respect to said abutments. Compression springs housed within said cages urge carbon rings into firm engagement with corresponding annular wedge-shaped Teflon rings the inner surfaces of which bear against the outer surface of the rotatable agitator shaft.
The structural details of the seal assembly are such as to require that the outer shell or housing be unbolted from the vessel and then removed upwardly from the sealing means on the agitator shaft so that the two metal cages in which the Teflon wedges, carbon rings, and spring assemblies are housed can be released from the agitator shaft and then slid upwardly off the upper end thereof.
In other words, to inspect and repair or replace the mechanical seal necessitates the upward withdrawal and bodily removal of the upper drive portion of the agitator shaft from the lower driven portion of said shaft.
U.S. Pat. No. 3,582,092 to F. J. Amorese and E. S. Harrison discloses a nonmetallic package rotary seal assembly for use in corrosive atmosphere wherein the end of the sleeve portion of the seal assembly which is exposed to the corrosive atmosphere is glass coated and is provided with a ceramic insert which forms a seat for containing O-ring means to seal the sleeve to the agitator shaft which extends through the seal. The shaft to be sealed is provided with an annular shoulder against which a shoulder of an elongate sleeve which is secured to and carried by the outer surface of the rotating shaft, is mounted. The outer surface of an elongate sleeve is engaged by a vertically spaced pair of wedge-shaped sealing means which are disposed in contacting relationship with the outer surface of the elongate sleeve by rotating seal members each of which have axial surfaces which are disposed in abutting relationship to an upper stationary outboard seal seat and a lower ceramic stationary seal seat wherein the wedge-shaped sealing members and their respective seal members are resiliently urged into rotary fluid sealing engagement with the aforesaid stationary seal seats.
The stationary seal seats, the rotating seal members, the wedge members, and the spring are all housed within a housing which is securely fastened relative to the drive nozzle of the vessel through which the shaft projects.
That portion of the upper end of the sleeve which projects outwardly beyond the upper end of the housing is adapted to be clamped directly to the agitator shaft whereby the sleeve, the wedge-shaped seals, the seal members, and spring are caused to rotate with the agitator shaft wherein the inner surface of the sleeve is sealed at its upper and lower ends to the outer surface of the agitator shaft by O-rings.
The lower end of the sleeve is provided with a ceramic insert which is bonded to and extends inwardly toward the shaft for defining an annular chamber into which the lowermost of the O-rings is received for engaging the shaft at a location adjacent but below an annular stop on said shaft. The seal, per se, cannot be removed endwise from a shaft along with or as part of the housing or chamber 16. The sleeve cannot be removed from the agitator shaft until after the housing has been detached from its connection relative to the drive nozzle of the reactor vessel. The sleeve sealing means which are located within the housing cannot be removed until after the housing has been completely removed from the agitator shaft since access to the interior of the housing is via its open bottom end only.
U.S. Pat. No. 3,877,706 of L. L. Haas discloses a mechanical seal assembly for glass lined mixer tanks wherein the component parts of the seal are housed within a cartridge which is supported as a unit package from a single component and whereby the unit package is removable as a unit by pulling it up slidingly along the agitator shaft of a reactor vessel. An elongate cylindrical spacer-and-support sleeve depends from and is secured in driven relationship from an upper cylindrical stationary seal having a lower axial seal face which is engaged by the upper axial seal face of a rotating seal member 51 which is housed within the upper collar portion of a spring holder and for endwise axial movement therein by means of a compression spring, and wherein said seal member includes an O-ring-receptive recess for disposing the O-ring in abutting relationship with an outer surface of the agitator shaft.
The spring holder likewise includes a second depending collar portion in which a second sealing member is mounted for endwise axial movement and whose lower axial surface is disposed in contacting relationship with the upper axial surface of a lower stationary sealing member which is sealed to the inner surface of an adaptor plate releasably secured to and carried by the flange of the nozzle of the reactor vessel in which the impeller shaft extends.
The spring holder is adapted to be securely, though releasably, anchored to the outer surface of the impeller shaft intermediate the location of the O-rings which are carried by the rotating seals. The lower stationary seal member is secured against rotation by a keyed engagement with the lower end of the cylindrical spacer and seal member.
A housing 3 contains the aforesaid seal means, said housing including means for introducing a lubricant interiorly of the housing for lubricating the mechanical seal between the aforesaid axial surface of the upper and lower rotating seal members with corresponding surfaces of the upper and lower stationary seal members. The O-rings which are secured to and carried by the rotating seal members prevent the lubricant from reaching the outer peripheral surfaces of the agitator shaft.
The entire seal assembly may be removed upwardly from the interior of the housing upon removal of a split annular top plate which spans the open upper end of the housing and the upper surface of the upper stationary seal force only after the drive means for the upper end of the agitator shaft has been removed for providing an unobstructed opening through the hollow quill sleeve drive the lower end of which is fixedly disposed in spaced relationship with a considerable length of the upper end of the agitator shaft, whereby the seal assembly, per se, can be pulled upwardly through the quill sleeve off the agitator shaft and thence out the upper end of the quill sleeve.